1. Field of the Invention
The present invention relates to liquid component concentration meters and, more particularly, relates to liquid component concentration meters including a light emission unit for irradiating light to a light transmission unit provided in a liquid supply tube, which is supplied with a liquid, a light reception unit for receiving light passed through the light transmission unit, and a data processing unit for calculating the concentration of the liquid based on the intensity of the light received by the light reception unit.
2. Description of the Related Art
As techniques for measuring the concentration of liquid in a tube, which is supplied with the liquid, there have been known liquid component concentration meters for optically measuring the concentration of liquid (refer to Patent Documents 1 and 2, for example). These liquid component concentration meters are generally inserted in tubes at their light transmission units made of glass, which are called “cells”. This is because, if measurements are performed directly on the liquids in the tubes, this will induce the problem of variations of the shapes of the tubes. Further, the tubes themselves may constitute the light transmission units, in some cases.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 11-14538    Patent Document 2: Publication of Japanese Patent No. 3290982
In cases of measuring the concentration of a liquid within a cell or a tube by irradiating and receiving light to and from the cell or the tube, with a liquid component concentration meter, there are the followings.
1) Measurement errors due to contaminations of the cell or the tube.
2) Measurement errors due to air bubbles adhered to the inside of the cell or the tube.
3) Measurement errors due to variations of the shape of the tube.
Regarding the liquid component concentration meter disclosed in Patent Document 1, in order to avoid the problem of adhesion of air bubbles to the inside of the cell, cells with complicated shapes are suggested.